President Trump last week revealed the U.S. Missile Defense Review (MDR), a congressionally mandated statement of U.S. policy to defend the United States, its forces and allies against missile attacks.

Here’s what we know about U.S. missile defense policy — and how to interpret the new MDR.

Missile defense sounds good — but there’s a catch

A quick review of U.S. strategic policy can be helpful. Defending the United States against a Russian or Chinese nuclear attack may seem like a no-brainer, but missile defense strategies can have dangerous consequences. In fact, during the Cold War, the United States and Soviet Union signed the Anti-Ballistic Missile (ABM) Treaty to ban the deployment of homeland missile defense systems.

This reassured arms-control advocates: With U.S. and Soviet homelands remaining vulnerable to a devastating counterblow, neither side was likely to launch a nuclear attack.

In 2002, the United States withdrew from the ABM Treaty so it could focus on defending against emerging missile threats from countries such as North Korea. But Washington reassured Moscow that missile defense deployments would remain limited and aimed only at smaller states.

The risk today is that both Moscow and Beijing may see any expanded missile defense as stepping up a suspected U.S. first-strike option — in a crisis, destroying their offensive nuclear forces by attacking them preemptively. Even if ineffective against a full Russian or Chinese attack, a large-scale defensive system could make a U.S. first strike easier by intercepting any retaliatory Russian or Chinese missiles.

This could prompt a new arms race, with U.S. adversaries building larger numbers of more capable missiles. And it could increase the incentives for Moscow or Beijing to attack the United States first with nuclear weapons during a crisis because any delay could lead to destruction of their own forces.

Why the Trump MDR marks a change

Some analysts suggested last year that the administration’s much-delayed MDR would see significant change in U.S. strategy — and a stepped-up effort against the forces of Russia and China.

We learned last week that the MDR stops short of advocating a large-scale U.S. missile defense system. But sections of the MDR suggest that the administration is laying the groundwork for a change in this direction.

The 2019 MDR includes subtle language shifts that push the benefits of missile defense, calling it a “stabilizing” technology because it would limit damage to the United States and its allies, while making a successful strike more difficult.

This moves away from the language of great-power reassurance the United States has used since 2001. Previously, the Obama administration claimed that Russia and China had nothing to fear because U.S. homeland defense systems were not capable of intercepting a major strike. The 2019 MDR states that, even if not very effective, U.S. homeland defense would be used to protect the country against an attack “from any source” — presumably including the two great powers. 

Shift to Russian and Chinese regional capabilities

The 2019 MDR places new emphasis on defense against Chinese and Russian regional missile capabilities — the systems with enough range to strike U.S. allies and deployed forces.

This is a policy change from the Obama administration’s 2010 Ballistic Missile Defense Review, which sought to cooperate with Russia on missile defense and, while reserving the right to defend against all missile threats in Asia, held out the prospect of dialogue with China on missile defense and strategic stability.

To deal with Russian and Chinese strategic nuclear forces designed to strike the United States, however, the 2019 MDR accepts that, for now, “the United States relies on nuclear deterrence” — the threat of nuclear war with Russia or China — to dissuade either power from attacking the United States. The administration’s short-term plans call for the installation of 20 additional interceptors at an existing facility in Alaska, radar upgrades and perhaps building one additional interceptor site — meaning that any protection of the U.S. homeland against Russian and Chinese missiles will remain extremely limited in the near term.

The MDR talks regional but looks to dual-use technologies

The long-term technological developments that the 2019 MDR sets in motion may raise questions about whether the new U.S. missile defense strategy is really aimed at regional defense or whether the ultimate goal is a defense against the strategic missiles Russia and China aim at the U.S. homeland.

The MDR lays the groundwork for considerable integration between regional and strategic missile defense systems — including an expanded role for the SM-3 interceptor, originally designed to deal with regional threats, to strengthen U.S. homeland defense during a crisis with a small nuclear power like North Korea. But the MDR’s statements about the possible role of homeland defense against Russia and China now make it likely that Moscow and Beijing will see this ambiguity between regional and strategic capabilities as a new threat to their strategic forces. The U.S. ambiguity may be a deliberate move, in the context of the administration’s emphasis on the value of missile defense in deterring attack through increasing adversary uncertainty.

The MDR also places new emphasis on exploring options to intercept ballistic missiles in the “boost phase” of flight — shortly after launch and while the payload has yet to deploy — enabled by a new space-based sensor layer. The MDR suggests this may include fitting interceptors to the F-35 fighter, laser-armed drones and even space-based interceptors.

The MDR emphasizes that these systems, if ever built, would be used only against rogue states. However, Moscow and Beijing are likely to remain skeptical because such a weapon could theoretically intercept advanced Russian and Chinese missiles.

And the MDR also outlines the need for greater integration of attack operations into U.S. missile defense planning — i.e., U.S. attempts to destroy enemy missiles before launch, in the case of “conflict with a rogue state, or within a region.” This raises the possibility of integration of strikes and missile defense to limit damage in a regional conflict with Russia or China.

But such planning highlights a fundamental problem with trying to defend against nuclear threats. What one country calls preemptive defense can look like an offensive first strike. The dividing line between a regional and strategic conflict is a matter of perception — and one that may not be shared by all sides, particularly if the United States is attempting to discriminate between regional and strategic missile forces in the fog of war.

James J. Cameron is a postdoctoral research associate in the Department of War Studies at King’s College London. He is the author of “The Double Game: The Demise of America’s First Missile Defense System and the Rise of Strategic Arms Limitation” (Oxford University Press, 2017). Follow @cameronjjj.